Discovery, Synthesis, and Evaluation of Highly Selective Vascular Endothelial Growth Factor Receptor 3 (VEGFR3) Inhibitor for the Potential Treatment of Metastatic Triple-Negative Breast Cancer

We herein report the identification,
structural optimization, and
structure–activity relationship of thieno­[2,3-d]­pyrimidine derivatives as a novel kind of selective vascular endothelial
growth factor receptor 3 (VEGFR3) inhibitors. N-(4-Chloro-3-(trifluoromethyl)­phenyl)-4-(6-(4-(4-methylpiperazin-1-yl)­phenyl)­thieno­[2,3-d]­pyrimidin-4-yl)­piperazine-1-carboxamide (38k) was the most potent VEGFR3 inhibitor (IC50 = 110.4 nM)
among developed compounds. Compared with VEGFR1 and VEGFR2, VEGFR3
was approximately 100 times more selective. Here, compound 38k significantly inhibited proliferation and migration of VEGF-C-induced
human dermal lymphatic endothelial cells (HDLEC), MDA-MB-231, and
MDA-MB-436 cells by inactivating the VEGFR3 signaling pathway. Additionally, 38k induced cell apoptosis and a prolonged G1/S-phase in MDA-MB-231
and MDA-MB-436 cells. It also presented acceptable pharmacokinetic
characteristics in Sprague-Dawley (SD) rats with an oral bioavailability
of 30.9%. In the xenograft model in vivo, 38k effectively inhibited breast cancer growth by suppressing the VEGFR3
signaling pathway. 38k pronouncedly resisted the formation
of pulmonary metastatic nodules in mice. Collectively, 38k may be a promising therapeutic agent of metastatic breast cancer.